Nandrolone Decanoate is a long acting depot; it takes quite a while for it to “kick in” and clear out of the system. Depending on how much is used; it will take at least 4-6 weeks after the last shot for Deca to clear out. It also takes about 4 weeks for active blood levels to stabilize. This can easily add up to 8-10 weeks of “dead time” . periods of time when blood levels are not consistent. These numbers apply to reasonable use of Nandrolone Decanoate; between 200-400mg a week. The more you use, the worst it gets. So a 10-week cycle of Deca can easily end up been a 16-week cycle when you account for clearance time (active blood levels). The first 4 weeks are also somewhat of a waste of time.
There are possible estrogenic side effects of Nandrolone despite it not being a very estrogenic hormone, at least not directly. Nandrolone does aromatize slightly. Aromatization refers to the conversion of testosterone to estrogen . This takes place when the testosterone hormone interacts with the aromatase enzyme. When the conversion takes place this can cause estrogen levels to go up, which can promote gynecomastia and water retention. High blood pressure can also become an issue if water retention becomes severe. Along with the low level of aromatase activity Nandrolone is also a progestin and has a strong binding affinity for the progesterone receptor. This may stimulate the mammary tissue and enhance the risk of gynecomastia in sensitive individuals.
Combating the estrogenic side effects of Nandrolone can be achieved by the use of anti-estrogen medications, specifically Aromatase Inhibitors (AI’s) such as Anastrozole ( Arimidex ). Selective Estrogen Receptor Modulators (SERM’s) are also sometimes used, such as Tamoxifen ( Nolvadex ). However, AI’s are the proper choice as they will directly reduce serum estrogen levels and SERM’s will not. An AI should be enough to reduce and avoid gynecomastia unless the individual already has existing gynecomastia that could potentially be exasperated.
Important Note: It’s often been said that Nandrolone based gynecomastia is based on increases in prolactin. It is true that 19-nor steroids can increase prolactin, which can also negatively affect libido and erection function. Some men may need to use a dopamine agonist to combat this. However, it is not prolactin that causes 19-nor based gynecomastia but rather the imbalance between estrogen and progesterone. If you merely combat prolactin you may find yourself with the very gynecomastia you tried to avoid.